[OpenSIPS-Users] rPort question

[José Pablo Méndez Soto]

Thanks a lot Bogdan.

I follow the use of rPort all the way explained here. What I don't
understand, is, if the received and rport parameters are filled in by the
UAS that gets the request, how is that useful to the UAC that originated it
when the reply is routed back to it? What situations may happen so that the
UAC needs this info?

NAT of course, but what would cause the SIP UAC not to process the reply
packet correctly? Is it the info contained at layer 5? or the socket
disruption at layer 3?

 *José Pablo Méndez
*********


2011/7/8 Bogdan-Andrei Iancu <bogdan at opensips.org>

> Hi José,
>
> 'rport' VIA param is to be used in NAT situations. As the VIA hdr is used
> for routing back the replies, if the caller is behind nat (and its VIA with
> a private IP), the routing back of the reply to it will not be possible.
>
> The way rport works it is very simple - this param (together with
> "received") are added to the top most VIA hdr if this VIA indicates a
> different IP:port than the src ip:port on net level. The received and rport
> are added to contain the layer 3 IP and port (which can be used later for
> routing back the reply).
>
> Regards,
> Bogdan
>
>
> On 07/06/2011 01:55 AM, José Pablo Méndez Soto wrote:
>
>> Hello,
>>
>> Can anybody explain how the rPort works in conjunction with STUN?
>>
>> I have gone through the RFCs but can't make sense out of  a packet capture
>> I have over here. If possible, I would like someone to explain how the layer
>> 3 and 5 IP addresses will flow and be re-writed when SIP works behind a NAT
>> (Just one side behind NAT  and the other publicly available lets say).
>>
>> Thanks in advance,
>>
>
> --
> Bogdan-Andrei Iancu
> OpenSIPS eBootcamp - 2nd of May 2011
> OpenSIPS solutions and "know-how"
>
>
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